Orthotic devices and appliances commonly referred to as “orthotics,” are known in the prior art and have been utilized for many years by doctors, orthotists, physical therapists and occupational therapists. They are primarily used to protect an injured or surgically repaired ankle or knee joint or a weakened joint caused by neurological disability or physiological deformity.
One such deformity is known as genu recurvatum of the knee. Genu recurvatum is a sustained posteriorly directed hyperextension moment of the knee joint (i.e., the knee bends backwards) occurring throughout the loading period of gait, from initial contact through forward progression. The posterior deviation of the knee joint (specifically in the tibiofemoral joint) disrupts normal gait and can negatively affect step length, stride length, gait velocity, walking cadence, increased lateral trunk displacement, and increased energy consumption while walking. If untreated, genu recurvatum can lead to significant knee joint deformities, which negatively affects walking ability and can predispose a patient to serious knee injury, knee pain and even cause knee osteoarthritis. Normal range of motion (ROM) of the knee joint is from 0 to 135 degrees in an adult. Full knee extension should be 0 degrees. In genu recurvatum normal extension is increased past 0 degrees.
The Swedish Knee Cage designed in the mid-1960s was the initial prefabricated commercially available knee brace to help control genu recurvatum. A typical Swedish Knee Cage brace design is a rigid “cage-like” unit that includes two upper lateral and medial uprights, two lower lateral and medial uprights and a generally U-shaped fixed posterior padded metal bar extending behind the knee. Also included are straps or cuffs and straps that secure the cage brace to the thigh and shin of a patient's leg. The padded metal bar is suppose to “block” or inhibit posterior movement of the knee joint. The metal “hyperextension stop” bar in some models is adjustable so that the brace fitter can stop the hyperextension of the knee at various positions depending on patient needs. Swedish Knee Cage designs all work as a physical block with a bar directly behind the knee to prevent movement backwards of the knee joint to simply control posterior movement of the knee. A typical Swedish Cage Knee Brace can be seen in U.S. Pat. No. 5,207,637 to Janke et al.
The Swedish Knee Cage design is essentially a static-design brace since the rigid component positioned behind the knee joint simply “blocks” the posterior movement of the knee joint. During the loading phase of gait, the knee joint of a genu recurvatum patient will move past neutral (i.e., straight leg) with the knee hyper-extending backwards away from the midline of the body. The rigid block positioned behind the knee stops posterior movement of the knee joint. The patient at the hyperextension moment of the “block” loses all inertia and must push off of the “block” to move forward. This creates a “halting” gait, wherein more time is spent on the affected leg with weight bearing than the unaffected leg during gait. This disrupts a normal gait pattern, requires significant additional energy to ambulate and can result in significant discomfort behind the knee when ambulating over extended distances.
Improvements are clearly needed in Swedish Knee Cage designed knee braces used in the treatment and support of the genu recurvatum.